Women who conceive within six months of an initial miscarriage have the best chance of having a healthy pregnancy with the lowest complication rates, according to a new study published on the British Medical Journal website.

Lead author, Sohinee Bhattacharya from University of Aberdeen, says that current World Health Organisation (WHO) guidelines recommending that women who experience a miscarriage should wait at least six months before getting pregnant again may need to be reviewed.

Women who experience a miscarriage are not only at an increased risk of a second miscarriage, says the study, but also of complications in a subsequent pregnancy. Around one in five pregnancies ends in miscarriage before 24 weeks.

But the length of time couples should wait before trying again to get pregnant are not consistent, say the authors, with some doctors saying there is no justification for asking women to wait and other bodies, such as the WHO, recommending a wait of at least six months. This study was based on women delivering in Scotland and while the findings are valid for this population, the original WHO guidelines may still be applicable to women in developing countries.

Delaying getting pregnant is particularly problematic in the western world, they add, because “women over 35 are more likely to experience difficulties in conceiving and women aged 40 years have a 30% chance of miscarriage which rises to 50% in those aged 45 years or more … any delay in attempting conception could further decrease their chance of a healthy baby.”

The researchers reviewed the data of over 30,000 women who attended Scottish hospitals between 1981 and 2000. The participants all had a miscarriage in their first pregnancy and subsequently had another pregnancy.

The results show that women who conceived again within six months were less likely to have another miscarriage, termination of pregnancy or ectopic pregnancy compared to women who got pregnant between six and 12 months after their initial miscarriage.

The women who conceived within six months were also less likely to experience a caesarean section, deliver prematurely or have low birth weight babies. This association wasn’t explained by social and personal factors or by other problems in pregnancy including smoking.

The authors conclude: “our research shows that it is unnecessary for women to delay conception after a miscarriage.” They add that when there are reasons to delay, for example if there are signs of infection, women should be advised about what to do to protect their health.

An accompanying editorial supports the view that women who conceive earlier may have better outcomes and fewer complications and calls for further research into this important area.